The use of fluoride chemicals in compositions for dental hygiene, such as mouth washes, tooth paste for daily care and dental prophylaxis cleaning compounds, has been known for some time. The known treatments include the use of soluble fluorides, such as sodium fluoride, and also the use of compounds containing stannous ion, such as stannous fluoride. Other sources of both stannous ions and fluoride ions have been used in various combinations, for example as combinations of stannous chloride and sodium fluoride. An abrasive material is also normally included in dentifrice compounds. The abrasive may be various insoluble phosphates, silicates, pumice flour, feldspar, zirconium silicate, silicon dioxide, or other abrasive materials, which if chosen with the proper particle size, are capable of cleaning and/or polishing the surfaces of teeth, without damaging the tooth structure.
It has also been known that there is a gradual loss of strength and anticaries effectiveness of stannous ions and fluoride ions in dentifrices, due to reactions which occur over time in the tooth paste or dental prophylaxis composition. For example, the stannous ions in an aqueous medium, such as tooth paste, may be gradually hydrolysed to stannic oxide or other stannic compounds which are insoluble and ineffective as anticaries agents. In addition, other complexes and insoluble compounds may be formed over time due to reactions which occur in the toothpaste medium so that the strength of the stannous ion may be considerably reduced prior to use of the tooth paste or dental prophylaxis paste.
Similarly, there is a loss of strength of the fluoride ion over time, particularly in an aqueous medium, due to the formation of insoluble reaction products with other chemicals which may be present in the medium. For example, the fluoride may react with a free calcium ion to form insoluble calcium fluoride, which is not effective as an anticaries agent. In addition, the fluoride may react with some humectants, such as glycerine, to form insoluble compounds which are not effective anticaries agents.
The art has taken numerous measures to compensate for or to minimize the reduction of strength of the anticaries agents over time. The art has tried to provide abrasives which are not contaminated by soluble calcium, for example, by attempting to procure and use abrasives, such as silicon dioxide or pumice, which are chosen to contain minimum amounts of available calcium. The art has also attempted to manufacture highly insoluble abrasives such as insoluble forms of calcium phosphate. These measures have been only partially effective. Over time, even insoluble forms of calcium phosphate release soluble calcium in sufficient quantity to react with fluoride. It is also extremely difficult to procure natural abrasives, such as silicon dioxide or pumice, which have a calcium content which is uniformly and acceptably low.
Another method of compensating for reduction of strength in dentrifrices containing anticaries agents has been to increase the content of those agents to a level considerably above their therapeutic optimum, realizing that the strength of these materials will be reduced over time. Enough of these materials are placed in the composition as a "safety factor" that even after some time the strength will remain at an acceptably high level.
Compensating for loss of strength by adding an incremental "safety factor" above the optimum level has created some problems, however, particularly in dental prophylaxis compositions. "Safety factor" quantities add a bad taste and may cause nausea and vomiting in some patients. This may be particularly true in combination with some abrasives, with which the effect may be quite pronounced.
With dental prophylaxis compositions, the art has used another tactic for minimizing the effect of time on the strength of the anticaries agents. The materials forming the dental prophylaxis dentifrice are supplied in two parts. One part is a dry powder containing the abrasive and ancillary compounds. The second part is a solution of the anticaries compound, for example an aqueous solution of stannous fluoride. The two parts are mixed just prior to use. This minimizes the reaction between the anticaries material and the abrasive, but does not eliminate the hydrolysis of stannous ions. Oxidation, formation of insoluble tin compounds and other reactions to reduce the strength of the anticaries compound can proceed. Moreover, this technique introduces a problem in handling, since it is necessary to measure the abrasive and the solution and then mix to form a paste. This is inconvenient, requires time, and may introduce errors in measurement and failure of complete mixing of the ingredients. Separation may occur in the solid ingredients over time, in the powder form, which affects the composition of the paste.
Applicant is aware of the following U.S. patents:
U.S. Pat. No. 2,876,168, PA1 U.S. Pat. No. 3,105,013, PA1 U.S. Pat. No. 3,105,798, PA1 U.S. Pat. No. 3,151,027, PA1 U.S. Pat. No. 3,257,282, PA1 U.S. Pat. No. 3,282,792, PA1 U.S. Pat. No. 3,330,732, PA1 U.S. Pat. No. 3,378,445, PA1 U.S. Pat. No. 3,445,567, PA1 U.S. Pat. No. 3,756,386, PA1 U.S. Pat. No. 3,804,946, PA1 U.S. Pat. No. 3,892,843, PA1 U.S. Pat. No. 4,016,255 and United Kingdom Pat. No. 845,611. The disclosures of the above patents are incorporated by reference herein.
Applicant has discovered a dentifrice composition that does not lose any substantial strength in its anticaries activity over time. In particular, applicant has provided a dentifrice composition that does not lose strength of stannous and fluoride ions due to reaction with time to form insoluble and unavailable compounds. Applicant's composition does not require a great excess of anticaries material and in particular does not require a great excess of stannous and fluoride ions to maintain a therapeutic level of the anticaries material over time.
Applicant's composition can maintain an effective level of anticaries material, such as stannous and fluoride ions, over time without requiring such a high initial level of these anticaries materials that the product has an unacceptably bad taste or causes unacceptable incidence of nauseous sickness or vomiting in patients on which the material is used.
Applicant's dentifrice can be supplied as a one component mixture in which all therapeutic and ancilliary ingredients are premixed and combined in dosage form and at dosage levels. Applicant's material does not require measuring and mixing of the therapeutic ingredients at or just before the use of the dentifrice. Applicant's composition does not require precise selection of abrasives, but can use any acceptable dental abrasive, cleaner or polisher without having extremely narrow tolerances for pure or highly insoluble material. Applicant's dentifrice can tolerate reasonable levels of soluble calcium without reduction in efficacy of the professional prophylaxis paste produced therefrom. Applicant's dentifrice can use any soluble dental therapeutic fluoride without extreme regard for taste of the same, since the material is not used in greatly excessive amounts, and can use any readily soluble dental stannous ion source without great regard to taste, since that also is not used in excessive amounts. The anticaries reagents used in the prophylaxis paste produced in the applicant's product are used at or near the optimum levels without any substantial loss of strength over time. The dental prophylaxis paste produced from applicant's dentifrice has excellent rheological properties for working with a standard dental prophylaxis cup.
Applicant's dental prophylaxis paste does not require that the therapeutic ingredients be mixed shortly prior to use. Substantially all of the preparation can be done long prior to use of the dentifrice. The dosage level is not subject to the errors of individual mixing and remains substantially uniform from one dosage unit to the next.
Applicant has provided a dental prophylaxis precursor or pellet which is readily hydratable with the addition of water to rapidly form a dental prophylaxis paste having abrasive and anticaries compounds and all necessary or desired ancilliary compounds such as flavorings, wetting agents and other materials.